Macrobrachium lanchesteri ( De Man, 1911 )

Hanamura, Yukio, Imai, Hideyuki, Lasasimma, Oulaytham, Souliyamath, Pany & Ito, Sayaka, 2011, Freshwater prawns of the genus Macrobrachium Bate, 1868 (Crustacea, Decapoda, Palaemonidae) from Laos, Zootaxa 3025, pp. 1-37 : 13-14

Macrobrachium lanchesteri ( De Man, 1911)

( Fig. 7 )

Palaemon paucidens: Lanchester 1901: 568 , pl. 33, fig. 4 (not De Haan). Palaemon (Eupalaemon) Lanchesteri De Man, 1911: 264

Macrobrachium lanchesteri: Holthuis 1950: 139 ; Chong & Khoo 1988: 196, figs. 1–3; Ng 1995: 252; Cai & Ng 2002: 77, fig. 19; Cai et al. 2004: 586.

Material examined. Luang Prabang Province: Ou River, Ngoi District, 11 males (CL 3.5–8.0 mm), 11 females (CL 6.5–7.5 mm), 8 ovig. females (CL 6.0–8.0 mm), 12 Aug 2000, coll. Somboon & Kaenchan; Pho stream, Na Pho Village, St. 5, 1 male (CL 6.5 mm), 28 Apr 2007, hand net, coll. S. Ito et al.; Pho stream, Na Pho Village, St. 5, 1 male (CL 7.0 mm), 30 Apr 2007, hand net, coll. S. Ito et al.; Pho stream, Na Pho Village, St. 5, 3 males (CL 7.2- 8.0 mm), 1 female (CL 11.0 mm), 6 ovig. females (CL 9.0– 10.2 mm), 26 July 2007, hand net, coll. S. Ito et al.; paddy field, Na Pho village, 2 females (CL 6.9 mm, 15.4 mm), 25 Jan 2008, hand net, coll. S. Ito et al. Vientiane Province: Pang River, Kasi District, 1 female (CL 7.8 mm), 29 Jan 2008, coll. local children. Vientiane Capital: Sivilay, 5 females (CL 4.5–6.0 mm), 1 ovig. female (CL 7.3 mm), 4 Aug 2007, coll. staff of NADC; Poxai Village, 2 males (CL 6.5, 6.6 mm), 1 female (CL 5.5 mm), 3 Aug 2007, coll. school children; Nanga Village, 2 males (CL 5.1 mm, 6.9 mm), 3 ovig. females (CL 6.1–7.8 mm), 17 Aug 2007, coll. school children; Nong Niew Market, 2 males (CL 4.5 mm, 5.6 mm), 3 females (CL 4.2–9.4 mm), 2 ovig. females (CL 7.8 mm, 9.4 mm), 31 Aug 2007, coll. H. Ikenoue; Nardi Village, 2 males (CL 6.0, 6.5 mm), 22 Sept 2007, coll. school children & H. Ikenoue; Nakha Village, 1 male (CL 6.8 mm), 2 females (CL 6.2 mm, 7.8 mm), 18 Nov 2007, coll. school children & H. Ikenoue; fish pond, NADC, Xuang River, 8 females (CL 5.8–7.8 mm), 7 Dec 2007, coll. H. Ikenoue: fish pond, NADC, Xuang River, 10 males (CL 4.0– 8.5 mm), 28 females (CL 4.2–10.8 mm), 10 ovig. females (CL 3.9–10.5 mm), 3 juv. (CL 1.8 mm), 18 Jan 2008, hand net, coll. Y. Hanamura & S. Morioka; Tham Village, 4 females (CL 6.6–8.0 mm), 1 ovig. female (CL 7.2 mm), 8 Dec 2007, coll. school children & H. Ikenoue; fish pond, NADC, Xuang River, 4 males (CL 4.0– 4.2 mm), 3 females (CL 4.4–5.3 mm), 30–31 June 2008, coll. H. Ikenoue (Id. by K. Hayashi). Champasak Province: Det Island, 3 males (CL 5.5–5.8 mm), 2 females (CL 7.5 mm, 8.0 mm), 21 July 2009, set net, coll. Y. Niimura; Det Island, 4 males (CL 8.8–10.0 mm), 6 females (CL 6.3–13.0 mm), 18 females (CL 8.2–12.2 mm), 21 July 2009, set net, coll. Y. Niimura.

Diagnosis. Rostrum ( Fig. 7 a) straight or weakly curving dorsad, barely reaching or extending slightly beyond antennal scale, armed dorsally with 5–10, commonly 7 or 8, teeth including 1 or 2 situated posterior to orbital margin and 0–2 placed near apex, ventral margin with 2–6, commonly 3–5, teeth; antennal spine marginal, extending well beyond antennal lobe: hepatic spine as large as antennal spine, placed posteriorly, just below level of antennal spine.

Sixth abdominal somite about twice as long as fifth, pre-anal carina indistinct but represented by obtuse ridge. Telson approximately 1.2 times as long as sixth abdominal somite, ending in sharp median projection, with 2 pairs of ordinary sub-terminal spines, 2 pairs of dorsolateral spines, anterior dorsal pair of latter ones placed at midlength of telson.

Antennal scale 0.8–1.0 times as long as carapace.

Second pereopods ( Fig. 7 a, b) slender, short, both legs similar in form and shorter than body, extending beyond antennal scale by slightly more than chela and onward; carpus slightly less than 1.5 times as long as chela; palm longer than fingers, latter with small tuberculate tooth near basal part. Third pereopod ( Fig. 7 c) with propodus 2.1– 2.5 times as long as dactylus.

Appendix masculina ( Fig. 7 d) slightly more than twice length of appendix interna, with somewhat sparsely scattered stiff setae on anterolateral margin as well as mesial surface. Exopod of uropod distinctly longer than endopod, movable spine on diaeresis ( Fig. 7 e) as long as or slightly shorter than lateral projection.

Egg. Eggs relatively larger in number, measuring about 0.6 x 0.9 mm in non-eyed eggs.

Remarks. The taxonomic status of M. lanchesteri has been reviewed by several researchers ( Chong & Khoo 1988; Cai & Ng 2002; Cai et al. 2004). In our observation, the second pereopods also showed some variations in the length of the carpus, owning possibly to ontogenetic growth, and smaller specimens tended to have a proportionately longer carpus than that observed in adults.

Breeding females bear smaller-sized, numerous eggs, and this is one of the important characteristics distinguishing this species from M. kistnense ( Tiwari, 1952) and M. tiwarii Jalihal, Shenoy & Sankolli, 1988 .

Distribution. Macrobrachium lanchesteri has been recorded with reasonable certainty from Peninsular Malaysia, Thailand, and Myanmar as well as from southern China and Java, and Indonesia (cf. Cai & Ng 2002; Cai et al. 2004). This species, one of the most common species in Laos, is frequently captured in ponds, paddy fields, and slow-flowing streams along the Mekong River system.

Figures

FIGURE 7. Macrobrachium lanchesteri, ovigerous female (CL 10.6 mm) (a, c, e) and male (CL 8.2 mm) (d) collected from Vientiane Capital, and female (CL 15.4 mm) (b) collected from Luang Prabang Province: a, entire body; b, chela of right second pereopod, mesial view; c, propodus and dactylus of left third pereopod, lateral view; d, appendix masculina, mesial view; e, uropodal diaeresis, lateral view.